Interface ArchetypeDataSource

Sources we can get Archetypes from. This may be the local registry, a Wiki, or,
a Maven Repository application. We might also want to get all the Archetypes based
on some predetermined criteria and that could be anything given the source. A simple
use-case might be to grab all Archetypes for a particular groupId, or Archetypes for
webapps, or who knows what.